A novel label-free and sensitive electrochemical biosensor for Hg2+ based on ligase-mediated formation of DNAzyme

• We report a label-free and simple electrochemical biosensor for Hg2+ detection.
• DNAzyme was formed through Hg2+ mediated DNA hybridization and ligase ligation.
• This biosensor exhibited excellent selectivity against other metal ions.

A novel label-free electrochemical biosensor for the detection of Hg2+ based on ligase mediated creation of G-quadruplex-hemin DNAzyme has been developed. Firstly, Cp probe was immobilized on the gold electrode surface through Au–SH bond. In the presence of Hg2+, Cp and Ap probes were partly hybridized with the LJ probe respectively through the specific T–Hg2+–T interaction. Then, the adjacent 3′-OH terminal of Cp will link with the 5′-PO4 terminal of Ap to form a G-rich DNA at the function of T4-ligase. After interaction with hemin, the G-rich DNA can form a G-quadruplex–hemin HRP-mimicking DNAzyme. Through measuring the current change caused by DNAzyme-catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine(TMB), sensitive detection of Hg2+ can be achieved. The proposed sensor is simple, sensitive and selective, without the need of complicated labeling process, thus holds great potential for routine analysis of Hg2+ in environmental and biological samples.

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